Spectre Staff

Every cast sends out a soul that curves toward the nearest enemy and drills through a couple of them before dying. The tracking is short ranged, though, so it is not a fire and forget weapon across a full screen: throw it into empty air and it will fly straight and hit nothing. Terrain stops the projectile dead, so you need line of sight the same as any other spell.

The Dungeon is where it earns its keep, since that is a place full of enemies coming around corners at eye level and the homing saves you from having to lead them.

• Its hits use their own immunity timer, so pairing it with a summon or a second weapon no longer causes the two to eat each other's damage.
• In player versus player the tracking is switched off, so it aims wherever you point it and nowhere else.
• The casters that drop it appear throughout the Hardmode Dungeon, so a farming run there gets you this and the rest of the tier at once.